Richtler et al., 2017, The globular cluster system of NGC 1316. IV. Nature of the star cluster complex SH2

# 세줄 요약 #

1. The light of the merger remnant NGC 1316 (Fornax A) is dominated by old and intermediate-age stars but the only sign of current star formation in this big galaxy is the Hii region SH2, an isolated star cluster complex.
2. We want to investigate the nature of this star cluster complex, so the nebular emission lines permit a metallicity determination that can discriminate between a dwarf galaxy or other possible precursors.
3. The high metallicity does not fit a dwarf galaxy as a progenitor that we favor the scenario of a free-floating gaseous complex having its origin in the merger 2 Gyr ago.

 

 

# 상세 리뷰 #

1. Introduction

• NGC 1316 (Fornax A) dominate by old & intermediate-age stars.
• SH2 (Hii region): The only current star formation region.
  • Age: estimate ~0.1 Gyr
  • Distance to galactic center: ~35 kpc

 

2. Method

• We used the Integral Field Unit (IFU) of the VIMOS instrument at the Very Large Telescope of the European Southern Observatory in high dispersion mode
  • to study the morphology, kinematics, and metallicity employing line maps, velocity maps, and line diagnostics of a few characteristic spectra.
• High resolution of Red & Blue mode: the spectra line flux map of SH2
• Diagnostic graph for six selected emission line spectra of SH2
  • estimated Oiii abundance to another line (Nii, Sii, ...).

 

3. Result

• Super-solar Oiii abundance 
  • -> SH2 is not infalling dwarf galaxy!
• molecular cloud complex scenario (SH2)
  • 1. formed during the merger ~2Gyr ago
  • 2. quiescent for a long time -> no external trigger event!
  • 3. started from star-forming at 0.1 Gyr ago

 

 

* Reference: Richtler, T., Husemann, B., Hilker, M., Puzia, T. H., Bresolin, F., and Gómez, M., “The globular cluster system of NGC 1316. IV. Nature of the star cluster complex SH2”, [Astronomy and Astrophysics], vol. 601, 2017. doi:10.1051/0004-6361/201630227.